1. Field of the Invention
The present invention relates to a channel access method and, more particularly, to a wireless communication system using channel access based on a contention approach and method thereof.
2. Description of Related Art
With the development of electronic technology, the types of the portable wireless devices change rapidly, and the needs for the portable wireless devices increase greatly. The important key to design the portable wireless devices is how to access channel bandwidth effectively, wherein one important means for allocating channel bandwidth is accomplished through a contention mechanism.
The challenge for applying the contention mechanism is how the channel requester, such as a laptop computer, quickly communicates with a channel allocator, such as an access point (AP) in a limited contention interval for transmitting data.
Currently, there are several multiplex channel access methods available. One is to use a statistics method to allocate and divide the channel bandwidth into a reserve bandwidth and a contention bandwidth to raise the performance of channel access; another one is to segment the contention time slots in two-dimension in accordance with the time and coding scheme to transmit data randomly; and the third one is to allocate a special communication channel for each communication device in accordance with an orthogonal frequency division multiplexing (OFDM) method to transmit the access request sent by the channel request.
All the above methods utilize non-overlapped contention time slots to contend for the communication resource. Such methods can raise the success rate of communication. However, in these methods, the quantity of the original contention time slots is restricted and thus the improvement in the success rate of communication is also limited. In addition, the above methods do not effectively utilize the time of the contention interval, which results in wasting the channel access and reducing the success rate of communication. Therefore, it is desired for the above methods to be improved so as to effectively allocate the contention time slots thereby increasing the performance of channel access.